Prof. Dr.-Ing. Norbert Vogt Chair of Foundation Engineering, Soil Mechanics, Rock Mechanics and Tunneling at the Technische Universität München

Implementation of Eurocode 1997-1 in Germany in Connection with a new DIN 1054 Athens, march 16th, 2009

Implementation of Eurocode 1997-1 in Germany in Connection with a new DIN 1054

Based on presentations of B. Schuppener, N. Vogt und A. Weißenbach

Implementation of Eurocode 7 in Germany • Introduction • Basic principle for the implementation (Î Selection of values of partial factors) • Three design approaches of EC 7-1 • Comparative design in an example • Conclusions of the comparative design (Î German selection of approaches) • Handbook of codes: DIN EN 1997-1 and its National Annex, which refers to a new DIN 1054

Basic principle for the implementation The former DIN 1054 was introduced in 1976 and is mandatory in all German federal states. ÎTradition, more than one generation ÎValidated: thousands of foundation constructions

The safety level of the former global safety concept shall be maintained when adopting the concept of limit state design and partial factors of the Eurocode!

Design approaches of EC 7-1 DA-1 Combination 1 Ed=E(γE>1)

DA-2

DA-3

Ed=E(γE>1)

Ed=E(γE>1)

Rd=R(γR>1, γϕ=1)

Rd=R(γR=1, γϕ>1)

Rd=R(γR= γϕ=1.0) Combination 2 Ed=E(γE=1) Rd=R(γR=1; γϕ>1)

DA 2 and DA 2*

Ed=E(γE>1)

bearing capacity is depending on - load inclination H/V - excentricity of loads e = M/V R = R(H/V; M/V; …) DA-2:

Rd=R(γR>1, γϕ=1)

DA-2*:

Rd = 1/γR·Rk Rd = 1/γR·Rk

Rk = R( Hd/Vd; Md /Vd; …) Rk = R( Hk/Vk; Mk/Vk; …)

With DA 2* all verifications are done with characteristic values of effects of action as far as possible. Application of partial factors to effects of action is the last step of verifications

Example for a comparison of the Design Approaches of EC 7-1 VG,k MH,k HQ,k

d

B=?m Depth of the strip footing: Permanent vertical effect of action: Variable horizontal action: Variable moment: Weight density of the soil: Angle of shearing resistance: partial factor for permanent/variable actions partial factor for bearing resistance partial factor for sliding

d = 1,0 m VG,k = 400 kN/m HQ,k gradually increased MH,k = 4.0 ⋅ Hk γ1 = γ2 =19 kN/m³ ϕ´k = 32.5° γG/Q = 1.35/1.50 γR;v = 1.40 γR;h = 1.10

6.00

Design Approach DA 1 comb. 1: γG = 1.35: Vk unfavourable comb. 1: γG,inf = 1.0: Vk favourable comb. 2: γϕ = 1.25, γQ = 1.30 global: η = 2.00

5.00 4.00

Width 3.00 B [m] 2.00

HQ,k/VG,k= 0.24 sliding becomes relevant

1.00 0.00 0

0.1

HQ,k/VG,k

0.2

0.3

6.00

Design Approach DA 2

5.00 4.00

(partial factors applied to the actions at the the beginning of the calculation ) γG = 1.35: Vk unfavourable γG,inf = 1.0: Vk favourable Global: η = 2.0

Width 3.00 B [m] 2.00

HQ,k/VG,k= 0.24 sliding becomes relevant

1.00 0.00 0

0.1

0.2

HQ,k/VG,k

0.3

6.00 Design Approach DA 2*

5.00

(partial factors applied to effects of actions at the end of the calculation) γG = 1.35: Vk unfavourable γG,inf = 1.0: Vk favourable

4.00

Global: η = 2.0

Width 3.00 B [m] 2.00

HQ,k/VG,k= 0.24 sliding becomes relevant

1.00 0.00 0

0.1

0.2

HQ,k/VG,k

0.3

7.00

Design Approach DA 3: γG = 1.35: Vk unfavourable γG,inf = 1.0: Vk favourable Global: η = 2.0

6.00 5.00 4.00

Width B [m] 3.00 HQ,k/VG,k= 0.21 sliding becomes relevant

2.00 1.00 0.00 0

0.1

HQ,k/VG,k

0.2

0.3

Summary • Maintaining the safety level of the former global safety concept is the basic principle in selecting the partial factors and the design approach in Germany. • The comparative design calculation for a strip footing showed that the safety level of the former global safety concept can only be maintained using design approach DA 2*. • Moreover, the comparative calculation showed that design approach DA 2* gave the most economic design.

Selection of values of partial factors EN 1990 gives the partial factors γF to be applied on actions and effects of action. To maintain the same global safety factors η as in advance, suited design approaches have to be chosen and partial factors γR to be applied on resistances to obtain: η = γF· γR

DIN EN 1997-1:2005 and DIN 1054:2005 DIN EN 1997-1:2005

Design approaches which are not used in Germany and informative annexes

DIN1054:2005

Common Regulations: e.g. Concept of limit states and partial factors, geotechnical categories

Specific German experiences: e.g. allowable bearing pressure, pile resistances

Relation between EN 1997-1 and national codes • Text passages of EC 7-1 may not be changed, i.e. nothing can be deleted and amendments are not allowed • Only at few distinguished points national choices can be made using the national annex • National codes will be allowed in the future but: • National Codes may not be contradictory to European Codes and may not be competing

National Annex to EN 1997-1 The national Annex contains: • Choices about design approaches to be applied • Regulations about the values of partial factors • Determinations about the use of informative annexes and • Links to non-contradictory additional informations, which may help the user in applying the Eurocodes – especially links to a new DIN 1054

DIN EN 1997-1

Eurocode 7: Entwurf, Berechnung und Bemessung in der Geotechnik - Teil 1: Allgemeine Regeln; Deutsche Fassung EN 1997-1:2005 DIN 1054

Baugrund – Ergänzende Regelungen zu DIN EN 1997-1:2005-10, Eurocode 7: Entwurf, Berechnung und Bemessung in der Geotechnik - Teil 1: Allgemeine Regeln DIN EN 1997-1/NAAdditional Regulations

Nationaler Anhang zu Eurocode 7: Entwurf, Berechnung und Bemessung in der Geotechnik - Teil 1: Allgemeine Regeln; Deutsche Fassung EN 1997-1:2005 National Annex

Normenhandbuch zu DIN EN 1997-1: 2005-10 Geotechnische Bemessung - Allgemeine Regeln und DIN 1054: 2009-xx Ergänzende Regelungen zu DIN EN 1997-1

Handbook of Codes

(DIN) EN 1997-1 German Annex to (DIN) EN 1997-1

DIN 1054: 2009 Additional regulations in connection of DIN EN 1997-1

Green text at left: National Annex

Black text in the middle: EC 7

Red text at right: Additional Regulations

Geotechnical Categories (GK) The Geotechnical Categories serve to determine minimal requirements with respect to - Soil Investigation, - Calculations and analyses - Control and measurements during construction time Definitions and examples are meanwhile harmonized in DIN 1054 und DIN 4020 (and other codes) The identical annex: „Examples of characteristics to classify into Geotechnical Categories“ will be used with DIN 1054 (design) and DIN 4020 (Soil investigation).

Design Situations • BS-P: Persistent Design Situation : this situation is in accordance with prevailing requirements to use a structure (previously it was loading case LF 1) • BS-T: Transient Design Situation : in accordance with temporal conditions and conditions which occur seldom or expectedly never (previously it was loading case LF 2, used for most construction situations) • BS-A: Accidential Design Situation : related to exceptional conditions for a structure (previously it was loading case LF 3) • BS-E: Earthquake Design Situation : (previously it was loading case LF 3)

Determination and Combination of Design Values of Effects of Action Ed = ∑ γ G, j ⋅ E(Gk, j ) + γQ,1 ⋅ E(Qk,1 ) + ∑γQ,i ⋅ ψ0,i ⋅ E(Qk,i ) j≥1

Ed

i>1

Design value of effect of action γG,j Partial factor for permanent effects of action E(..) Effect of action resulting from (..) Gk,j Characteristic value of a permanent action γQ,i Partial factor for variable effects of actions Qk,1 Characteristic value of the leading variable action ψ Combination factor Qk,j Characteristic values of accompanying variable actions

Determination and Combination of Design Values of Effects of Action where superposition is not possible

Ed = E( ∑ γ G, j ⋅ Gk, j "+" γ Q,1 ⋅ Qk,1 "+" ∑ γ Q,1ψ 0,i ⋅ Qk,i ) j≥1

i>1

„+“ „is to be combined “, Σ: „joint effect of “ Ed Design value of effect of action E(..) Effect of Action resulting from (..) γG,j Partial factor for permanent actions Gk,j Characteristic value of a permanent action γQ Partial factor for variable actions Qk,1 Characteristic value of the leading variable action ψ Combination factor Qk,i Characteristic values of accompanying variable actions

Limit States according to DIN 1054:2005 Three limit states with different use of partial factors LS 1A: Partial factors only to be used on actions (to be used with overturning, uplift and buoying upwards) LS 1B: Partial factors to be applied on effects of action and resistances; ( to be used with verifications of constructions and parts of construction) LS 1C: Partial factors to be applied on actions and on shear resistance (to be used with verifications of slope stability and overall stability)

Limit States according to EN 1997-1 DIN EN 1997-1 EQU

UPL

HYD

DIN 1054

Limit State

LS 1A

Loss of equilibrium of the structure or the ground, in which the strengths are insignificant in providing resistance.

LS 1A

Loss of equilibrium of the structure or the ground due to uplift by water pressure (buoyancy) or other vertical actions.

LS 1A

Hydraulic heave, internal erosion and piping in the ground caused by hydraulic gradients

LS 1B

Internal failure of the structure or ist parts, in which the strength of structural materials is significant in providing resistance.

LS 1C

Failure or excessive deformation of the ground, in which the strength of the ground is significant in providing resistance.

STR GEO-2 GEO-3

Partial Factors for Actions in Germany Action and Effects of Action

1054 old new

(LF 1) BS-P

(LF 2) BS-T

(LF 3) BS-A

Hydraulic Failure and Uplift (buoyancy) (HYD and UPL) Destabilising Permanent Actions

γG,dst

1,00 1,05

1,00 1,05

1,00 1,00

Stabilising Permanent Actions

γG,stb

0,90 0,95

0,90 0,95

0,95 0,95

Destabilising Variable Actions

γQ,dst

1,00 1,50

1,00 1,30

1,00 1,00

Failure of Stuctures and Ground (STR und GEO-2) Effects of Action due to Permanent Actions

γG

1,35

1,20

1,00 1,10

Effects of Action due to Variable Actions

γQ

1,50

1,30

1,00 1,10

Partial Factors for Soil Resistances Design Situation BS-P

BS-T

BS-A

γϕ, γϕu

1,25

1,15

1,10

γc, γcu

1,25

1,15

1,10

GEO-3: Limit State by loss of overall stability tan ϕ′ of drained soil; tan ϕu of undrained soil cohäsion c′ of drained soil and shear strength cu of undrained soil

Partial Factors for Resistances Design Situation

Resistance

BS-P

BS-T

BS-A

STR und GEO-2: Limit state of failure of constructions, parts of construction and ground

Ground Resistance earth pressure resistance and bearing resistance Resistance against sliding

γR,e, γR;v

1,40

1,30

1,20

γR,h

1,10

1,10

1,10

Pile Resistance based on static and dynamic pile loading tests Base Resistance

γb

1,10

1,10

1,10

Shaft Resistance (Compression)

γs

1,10

1,10

1,10

Total Resistance (Compression)

γt

1,10

1,10

1,10

Shaft Resistance (Tension)

γs,t

1,15

1,15

1,15

Compression Piles

γb; γs; γt

1,40

1,40

1,40

Tensile Piles (only in exceptional cases)

γs,t

1,50

1,50

1,50

Soil-Nails and Rock-Nails

γa

1,40

1,30

1,20

Bodies of grouted anchors

γa

1,10

1,10

1,10

Flexible reinforcement elements

γa

1,40

1,30

1,20

Pile Resistance based on Experience

Pull-Out-Resistance

Partial Factors for Pile Resistance Resistance

1054 old new

(LF 1) BS-P

(LF 2) BS-T

(LF 3) BS-A

Pile Resistance based on static Pile Loading Tests Base Resistance

γb

1,20 1,10

1,20 1,10

1,20 1,10

Shaft Resistance (Compression)

γs

1,20 1,10

1,20 1,10

1,20 1,10

Total Resistance (Compression)

γt

1,20 1,10

1,20 1,10

1,20 1,10

Shaft Resistance (Tension)

γs,t

1,30 1,15

1,30 1,15

1,30 1,15

1,40 1,40 1,50

1,40 1,40 1,50

1,40 1,40 1,50

Pile Resistance based on Experience Compresion Piles Tensile Piles (only in exceptional cases)

γb, γs, γt γs,t

Recommendations concerning Piles

Links to these recommendations are given in DIN 1054:2009

Links to further recommendations: EAB concerning excavation pits

Will also be available in English

Simplified Verification for Shallow Footings Table A 6.7: Design Value of Bearing Resistance σR,d for Strip Foundations on Clay and Silt (UM, TL, TM) Embedment depth of the footing

Design Value of Bearing Resistance σR,d kN/m2 Consistency

m

Ic > 0.75

Ic > 1.0

Ic > 1.25

0,50

170

240

390

1,00

200

290

450

1,50

220

350

500

2,00

250

390

560

120 bis 300

300 bis 700

> 700

Uniaxial Compression strength qu,k in kN/m2

Attention: the values are not allowable bearing pressures!

Limit State or

1A / EQU, UPL, HYD (Problem of Equilibrium) 1B / STR (Strength of the Construction) 1C / GEO (Failure of the Ground) ?

Overturning and Gap in Base Joint

Overturning related to destabilising: Mdst,Q,k = 80 · 7,0 = 560 kNm stabilising: Mstb,G,k = 300 ⋅ 2,8 = 840 kNm Î Md,Q,dst = 1,50 ⋅ 560 = 840 kNm Md,G,stb = 0,90 · 840 = 756 kNm (< Md,Q,dst)

7,0 m

Verification of Gap in Base Joint; : Mk = 80 · 7,0 = 560 kNm Vk = 300 kN/m Excentricity: e = 560 / 300 = 1,87 m Maximum of Gap: Centre of footing: e < b/3 b/3 = 5,6 / 3 = 1,87 m Verification is ok

Hk = 80 kN

Gk = 300 kN 5,6 m

γQ,dst = 1,50 γG,stb = 0,90

Verification is not ok. Footing must be enlarged. As the geometry of a footing can be determined by this verification, DIN 1054:2009 requires this verification, although overturning over an edge is physically not possible: ground failure will occur before overturning

Verification of foundations with intensive excentric loading VG,k MQ,k e ≤ b/3 b/3

b/2

Global Safety against Overturning: η = 1,50 =

V ⋅ b/2 V ⋅ b/3

Limit State of Static Equilibrium EQU with γQ,dst = 1,50 and γG,stb= 0,90 Î η = γQ,dst / γG,stb = 1,67 Î Both verifications are necessary with DIN 1054:2009

Overturning and Verification of reinforced concrete structure of a footing

Verification is ok. With this enlarged footing verification of reinforced concrete structure of the footing can be done with a (fictive) ground pressure distribution within the area of the footing Md = 80·7,0·1,50 = 840 kNm

Gd = γG,inf · Gk 1,00 · 300 kN

Hk = 80 kN

7,0 m

enlarged footing, B = 6,4 m Verification of overturning related to destabilising: Mdst,Q,k = 80 · 7,0 = 560 kNm stabilising: Mstb,G,k = 300 ⋅ 3,2 = 960 kNm Î Md,Q,dst = 1,50 ⋅ 560 = 840 kNm Md,G,stb = 0,90 · 960 = 864 kNm (> Md,Q,dst)

Gk = 300 kN 6,4 m

γQ,dst = 1,50 γG,stb = 0,90 γG,inf = 1,00

(γG,sup = 1,35) e = 840 / 300 = 2,8 m σ = 300 / ((3,2-2,8)·2) = 375 kN/m2

σ e = 2,8 m

Verifications of block foundations with intensive excentric loading

Ep,mob ≤ 0,25 ⋅ Ep,k Ep,mob Ep,k

Mobilised Part of the Characteristic Passive Earth Pressure Characteristic Passive Earth Pressure

Anchorages •

There are some national additional rules for all kinds of anchors within DIN 1054

•

Forces to be applied within suitability tests and acceptance tests : Pp = 1,1 ⋅ Pd Pp Maximum Force within the tests Pd design value of the effect of actions of anchors

•

Details concerning testing of anchors are given in DIN EN 1537 and a national additional code

Failure of walls embedded in soil due to vertical movement

Roughness of the wall

Bv,k = Bh,k⋅ tan δB

Bv,k

Interlocked wall

| δa | ≤ ⅔∙φ'k | δB | ≤ φ'k

Rough wall

| δa | ≤ ⅔∙φ'k | δB | ≤ φ'k - 2,5° and | δB | ≤ 27,5°

Not so rough wall

| δa |≤ ½∙φ'k

| δB | ≤ ½ ∙ φ'k

Plain wall

| δa | = 0

| δB | = 0

δa

δB

Eav,k

Eav,k= Eah,k⋅ tan δa

Efcharisto poli